., massachusetts institute of technology and campus police officer was killed by these two suspects. these two brothers. one 19 years old. one 26. a carjacking, they stole a car. that individual whose car it was, was kept with them. h miraculously was let free. they identified themselves as the boston marathon mom bombers in the car. that man escaped. in the police pursuit of these individuals, there was a shoot-out. older brother, 26 years old, mortally wounded, taken to beth israel hospital. there he was pronounced dead. the doctors there said he had wounds both from burns, from explosives and bullet wounds. wouldn't say which was fatal. >> key distinction. they don't know when he got the burns. from the altercation from police or because he was, in fact, connected to the attack at the marathon. >> we have also heard in the pursuit two of the brothers, the younger brother, 19-year-old, ran over his older brother according to one source. we should caution everybody, this is all early, developing information as we've learned. the first stories we hear, even from law enforcement, are